Lightning

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LIGHTNING GROUNDING YOUR BOAT open water This same study listed an additional
177 who were injured while on or near can kill Carrying as much as 100 million
waters Water and lightning are a natural combi 60
volts lightning can smash a hole through a hull
a mast and electrocute several people in
a single flash The thunderstorms of the
WHAT CAN YOU Bay described by Captain John
Smith as among the most violent he had ever To protect yourself in a boat the important thing is
seen pose a lightning threat every boater should to give lightning a ground Boats made of steel
know about such as naval vessels have an automatic ground
in their metal hulls but most small boats usually
WHAT IS LIGHTNING constructed of fiberglass or wood prevent the
Lightning is simply natures way of equalizing con lightning easy access to the water and pose a
trasting charges often built up when cool and grounding problem Small boats may also lack tall 60
warm air masses collide As negative charges in objects which could deflect lightning and even
the base of a storm cloud pass over the earth boats that do have tall spars like sailboats
they induce a positive charge in the normally neg can run into problems if their spars are not prop
atively charged terrain This positive charge actu erly grounded The following grounding system
ally works its way up tall objects pulled by the will minimize the risk of lightning clouds When an arc breaks
Grounded spars or antennas offer a 60 degree cone of
through the insulating air lightning strikes Not all On a sailboat make a lightning rod using a piece protection Note that this cone
measures from the follows the same scenario It can leap of aluminum which sticks about 1 foot 3048 cen point off the water not from a
masts full height Since
from cloud to cloud from cloud to earth or from timeters above the mast Sharpen the rod to boats usually heel during storms the
cone of protection
reduce resistance at the top A radio antenna can will shrink proportionate to the dip of the mast A bending
earth to cloud or slanting whip antenna will
considerably lesson the pro
also conduct electricity but may lead lightning to tected zone as the illustration shows Adapted from the
HOW DANGEROUS IS LIGHTNING the radio and may well vaporize during a strike National Fire Protection Code
In the United States lightning kills over time From the rod lead a wire down a wooden mast
more people than do hurricanes floods or torna an aluminum mast can serve as its own conductor On a motorboat which has no high spar
use a
does Although lightning rarely reaches the cata as long as a wire is led from its base to direct the metal radio antenna not a fiberglass
one dimensions that make headlines it con charge to the ground A wooden mast with a ing a wire to a ground plate as described
kills over a hundred people a year in this metal sail track can be grounded as though it If there is a loading coil on the antenna use a
country Not everyone struck by lightning dies were a metal mast The Coast Guard finds a 8 shunt of 31strand 17gauge bare estimate
that twothirds of those wire adequate though a larger gauge say 4 grounding mesh to bypass it this will make the
struck by lightning survive and often people further reduces heat and resistance whole height of the antenna an
effective killed by a lightning strike can be Quickrelease clamps will allow an easy
by But Attach this wire to a copper ground plate mounted rary attachment On a fiberglass antenna you
risks remain high for those who spend time out on the hull beneath the waterline or dangled can clamp the wire to a metal rod
letting that act
doors farmers fishermen or boaters underwater A square foot of copper flashing eas as a lightning interceptor Use a lightning
ily obtained at many hardware stores will make arrestor to protect your water conducts electricity so well and an adequate ground
plate If you decide to a boat or even a person may pres a permanent ground use large stainless steel When leading the wire to a
ground avoid sharp
ent a high profile on water boaters need to take bolts say 12 inch to prevent their cracking under bends or turns Any bend in the wire
should have
special precautions Records show that lightning large electrical discharge To increase safety a radius of at least 60 degrees
has killed people who were standing in or fishing some recommend all stays be grounded to the
from boats or starting outboard motors One study plate One alternative calls for leading the
that out of 494 people killed while involved wire to a metal strip which runs down the
bow or
in outdoor recreation 200 were in on or near stern and maintains constant contact
with the
water This offers the advantage of carrying the lence Remember that lightning can lash out for
at a gradual angle safely away from the miles in front of a storm and it can strike after a
engine and the helm storm has seemingly passed Remember too
that storms can bring high winds and waves
Both the mast and the whip antenna will provide a making a last minute trip to shore a of protection with a radius of approximately dash The
best maneuver of all is to think ahead
the same dimension as the rods height For most
small boats this will include the entire deck area may be however induced electrical by the lightning and for this reason large objects
engines for example should avoided during a storm Remember that an will have its own ground in the propeller
the shaft Induced electrical charges can
arcing and electrical shocks strong enough shtm
to knock you unconscious perhaps heart arrhythmias A lightning strike University of Florida Sea Grant Lightning and Sailboats
can also magnetize a keel or other metal fittings video and booklet booklet alon your compass useless AID FOR LIGHTNING
Please note that no system is full proof According to the American Boat
After a shipboard lightning strike check to see and Yacht Council Inc In view of the wide variation in structural
design of boats and the unpredictable nature of lightning specific rec
that everyone is all right it is of course per ommendations cannot be mae to cover all safe to handle someone who has been hit
by lightning Check for burns which should Marine Advisory Program First published normal first aid treatment Dont put oint
ment on severe burns cover them with clean
cloth or plastic to keep out air
If someone has been knocked unconscious Check for breathing and you feel a pulse but no breathing begin resuscitation a handkerchief over the
mouth will help the squeamish If there is no
heartbeat begin a
technique every serious boater should your boat and unplugging radios equipment during a storm are good
ideas but the best precaution against lightning is
avoidance Especially in small craft keep a
weather eye out for the coppery haze and build
GROUNDING
ing cumulonimbus clouds that signal heading ashore well ahead of the turbu
YOUR BOAT

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